Method of quenching and quenching liquid



United States Patent 3,022,205 IVIETHOD OF QUENICIHIN G AND QUENCHING QFrederic L. Chase, Dayton, and Charles W. Ewing, Centerville, Ohio,assignors to General Motors Corporatron, Detroit, Mich., a corporationof Delaware No Drawing. Filed May 14, 1958, Ser. No. 735,115 8 Claims.(Cl. 14820.6)

definite temperature and then cooled. In many of such heat treatingoperations, the hot metal is cooled more or less rapidly and such rapidcooling operations aregenerally known as quenching. Generally, quenchingis accomplished by immersing the hot metal in a bath of a liquid such aswater or oil. A common quenching operation is the quenching of steel inwater or other aqueous liquids or in oil to harden the'steel.

Water, which is the cheapest quenching liquid and which produces veryrapid cooling, is not suitable for quenching many kinds of steel. Inmany steel heat treatment operations, the steel is quenched in ahycrocarbon oil which gives a relatively slow rate of cooling, which isrequired to produce certain desired physical properties such as hardnessand ductility. Rapid'cooling caused by water quenching insteel'hardening operations results in excessive strains in certain kindsof steel which warp and crack the steel. The slower cooling rateafforded by oil quenching prevents such excessive strains but often doesnot develop maximum hardness. It, therefore, is desirable to providequench liquids which will cool the metal at rates intermediate betweenoil and water quenches, whereby the greatest degree of hardness can beobtained without warping or cracking the steel. Oil quenching isexpensive, not only because of the initial cost of the oil, but alsobecause the oil deteriorates in use and must be refined or replaced withfresh oil. The flammable nature of hydrocarbon oils also presents aserious fire hazard in oil quenching operations. The art has long soughtfor cheap substitutes for oil but without much success. Aqueoussolutions of salt or caustic soda, which are used to some extent,provide an even faster rate of cooling than water and are not suitablefor use where a cooling rate intermediate between those obtained inwater and oil is desired. Various aqueous solutions or dispersions oforganic materials such as starch, glue, pectin, natural gums and thelike, have been from time to time proposed as steel quenching liquids,but these have not proved successful as substitutes for quenching oilssince they are erratic and unpredictable in their quenching propertiesover even a short period of usage.

It is an object of this invention to provide a new and useful processfor quenching metals in heat treating which has no fire hazards,oifensive odors, fumes or foaming problems and which is substantiallyuniform in quenching effect over long periods of usage, stable, longlived, low in cost, and can be used at various temperatures and can bevaried to provide different advantageous quenching rates.

It is another object of this invention to provide an aqueous quenchingsolution whose strength can be varied to provide a broad range ofadvantageous predictable quenching rates between the quenching rates ofwater and oil which rates are substantially uniform over a long periodof usage and which has no fire hazards, oifensive odors, fumes orfoaming problems and is low in cost,

7 long lived, stable, and can operate at a variety of usefultemperatures.

It is another object of this invention to provide such a process andsolution with an inexpensive rust inhibitor which will pacify ortranquilize this solution and which will not affect undesirably theprocess or solution or make the quenching rates erratic. v J

Generically, to attain these and other objects, metal such as carbonsteel, oil hardening grade steel or car-, bonized steel are heated abovetheir critical temperature and then quenched in an aqueous solutioncontaining .2 to 4 grams per gallon of water of a high polymer ofethylene oxide having molecular weights from 100,000 up to severalmillion. The concentration is varied inversely according to the rate orspeed of quenching desired. No other additive is required in thesolution unless the tank and other parts of the quenching apparatuscoming into contact with the solution are subject to rust. To preventrusting of the tank. or other apparatus, a rust inhibitor is used whichhas a pacifying or tranquilizing action upon the solution so that itdoes not'makegthe quenching propertie erratic. Suitable rust inhibitorswhich maybe added are mono-, di-, or tri-ethanolamine in amounts ofabout /2 by weightor sodium, potassium or amonium borate in amounts ofabout 1 by weight. These amounts are sufiicient to prevent rusting ofthe parts and apparatus; I As one specific example of the invention,hexagonal billets, of an inch across the flats and 2%- inchesrlong ofSAElCl144 steel, were heated tol52'5 F. and then quenched in a steeltank containing one gallon of aqueous solution whose temperature waskept at F. or below. The critical temperature of this steel is aboutIAOOYF. The solution contained /2 a gram of a very high polymer ofethylene oxide having a molecular weight of several million known asPolyox 701. Preferably, the solution also contains /2% by weight oftriethanolamine, which not only inhibits rusting of the steel tank, butalso acts as a pacifier or stabilizer promoting smoothness and quiet,orderly boiling of the solution. This solution and this processuniformly hardened the billets over an extended period of usage,obtaining the desired degree of hardness without warping or cracking. Ithas no fire hazard, ofiensive odors, fumes or foaming problems. It islower in cost than any other comparable quenching solution exceptingwater and can be used without replacement for long periods of time.Therquenching rate is stable and predictable.

To obtain a more rapid quenching rate, a lower concentration solutionmay be used as low as .2 of a gram per gallon while to obtain a slowerquenching rate, a higher concentration solution up to 4 /2 grams pergallon of high polymer ethylene oxide may be used. The desirableconcentration of the polymer is less when the molecular weight is high.

When the polymer having molecular weights of several million (Polyox701) is used, the desirable concentration varies from .2 to 1 gram pergallon.

When polymers of lower molecular weights, such as 1,000,000 to 100,000,are used, higher concentrations are desirable. For the grade Polyox 301,the desirable range is about .6 to 2 grams per gallon. For the gradePolyox 205, the desirable concentration is about 1 to 2 /2 grams pergallon. For the grade Polyox 35, the desirable concentration is about2V2 to 4% grams per gallon.

If a lower cost solution is desired, borax in an amount of about 1% byweight may be substituted for the triethanolamine. It also has apacifying and transquilizing effect upon the solution, but this effectis less than the corresponding effect of triethanolamine. The solutionalso prevents rusting of the steel parts and provides the parts with athin protective coating.

)2, An improved method for quenching heated metal' which comprisesquickly immersing said heated metal in a liquid bath consistingprincipally of an aqueous solution of a watersoluble high polymerofethylene oxide and a rust inhibitor, said polymer having a molecularweight between 100,000 and several million. a a

3. An improved method for quenching heated metal which. comprisesquickly immersing said heated metal in a liquid bath consistingprincipally ofan aqueous solution containing between 350 gram and 4%grams of a water soluble high polymer of ethylene oxide per gallon ofwater having a molecular weight between 100,000 and several million andabout one percent by weight of borax.

4. An improved methodfor quenching heated metal which comprises quicklyimmersing said heated metal in aliquid bathconsisting principally of anaqueous solution borax.

ular weight between 100,000 and several million, and a 'rust inhibitor.

6. A quenching liquid for: the heat treatment of materials consistingessentially of water containing between gram and 4 /2 grams of a highpolymer of ethylene oxide per'gallon of water, said polymer having amoiecular weight between 100,000 and several million," and Aquenching'liquid for the heat treatment of materials consistingessentially of water'containing between $1 gram and 4 /2 grams of'apolymer of ethylene oxide per gallon of water, said polymer having amolecular weight between'l00,000 and several million.

containing bctwcengi gram and 4 /5 grams of a water soluble high polymerof ethylene oxide'per gallon of water having a molecularrweight between100,000 and several'millionand about' l percent by weightofrtriethanolamine.

5; A'quen c'hing liquid for the heat treatment of mat'erialsfconsi'stingessentially of water containing between gidgr'am and 4% grams of a highpolymer of ethylene oxide per gallon of water, said polymer having amolec- 8. A quenching liquid for the heat treatment of ma terialsconsisting essentially of water containing between 3 gram and 4 /2 gramsof a polymer ,of ethylene oxide per gallon of water, said polymer havinga molecular weight between 100,000 and several million and about /2.percent by weight of triethanolarnine. V

References Cited in the file ofthis patent UNITED STATES PATENTS2,793,147 Erdmann et a1 May 21, 1957 2,799,606 Freeman July 16, 19572,914,491 Bailey Nov. 24, 1959 FOREIGN PATENTS Y 716,354 Great Bri tain"Oct. 6, 1954 OTHER REFERENCES Ethers and Oxides, by Carbide and CarbonChemicals- Corporation. Pages 12 -13. Library call -Number TP 248; E7. VV

Ucon Booklet by Carbide and-Carbon Chemicals Corporation,j2 0 pages,pages '14, 15 and l7 relied upon. Library c'all Number TP 247 C32.

.Corneil June 10, 1952

1. AN IMPROVED METHOD FOR QUENCHING HEATED METAL WHICH COMPRISES QUICKLYIMMERSING SAID HEATED METAL IN A LIQUID BATH CONSISTING PRINCIPALLY OFAN AQUEOUS SOLUTION CONTAINING BETWEEN 2/10 GRAM AND 4 1/2 GRAMS OF AWATER SOLUBE HIGH POLYMER OF ETHYLENE OCIDE PER GALLON OF WATER, SAIDPOLYMER HAVING A MOLECULAR WEIGHT BETWEEN 100,000 AND SEVERAL MILLION.